Repo created

TMessagesProj/jni/voip/webrtc/base/threading/thread_checker.h

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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_THREADING_THREAD_CHECKER_H_
+#define BASE_THREADING_THREAD_CHECKER_H_
+
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+#include "base/strings/string_piece.h"
+#include "base/thread_annotations.h"
+#include "base/threading/thread_checker_impl.h"
+
+// ThreadChecker is a helper class used to help verify that some methods of a
+// class are called from the same thread (for thread-affinity).  It supports
+// thread safety annotations (see base/thread_annotations.h).
+//
+// Use the macros below instead of the ThreadChecker directly so that the unused
+// member doesn't result in an extra byte (four when padded) per instance in
+// production.
+//
+// Usage of this class should be *rare* as most classes require thread-safety
+// but not thread-affinity. Prefer base::SequenceChecker to verify thread-safe
+// access.
+//
+// Thread-affinity checks should only be required in classes that use thread-
+// local-storage or a third-party API that does.
+//
+// Prefer to encode the minimum requirements of each class instead of the
+// environment it happens to run in today. e.g. if a class requires thread-
+// safety but not thread-affinity, use a SequenceChecker even if it happens to
+// run on a SingleThreadTaskRunner today. That makes it easier to understand
+// what would need to change to turn that SingleThreadTaskRunner into a
+// SequencedTaskRunner for ease of scheduling as well as minimizes side-effects
+// if that change is made.
+//
+// Usage:
+//   class MyClass {
+//    public:
+//     MyClass() {
+//       // It's sometimes useful to detach on construction for objects that are
+//       // constructed in one place and forever after used from another
+//       // thread.
+//       DETACH_FROM_THREAD(thread_checker_);
+//     }
+//
+//     ~MyClass() {
+//       // ThreadChecker doesn't automatically check it's destroyed on origin
+//       // thread for the same reason it's sometimes detached in the
+//       // constructor. It's okay to destroy off thread if the owner otherwise
+//       // knows usage on the associated thread is done. If you're not
+//       // detaching in the constructor, you probably want to explicitly check
+//       // in the destructor.
+//       DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
+//     }
+//
+//     void MyMethod() {
+//       DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
+//       ... (do stuff) ...
+//     }
+//
+//     void MyOtherMethod()
+//         VALID_CONTEXT_REQUIRED(thread_checker_) {
+//       foo_ = 42;
+//     }
+//
+//    private:
+//     int foo_ GUARDED_BY_CONTEXT(thread_checker_);
+//
+//     THREAD_CHECKER(thread_checker_);
+//   }
+
+#define THREAD_CHECKER_INTERNAL_CONCAT2(a, b) a##b
+#define THREAD_CHECKER_INTERNAL_CONCAT(a, b) \
+  THREAD_CHECKER_INTERNAL_CONCAT2(a, b)
+#define THREAD_CHECKER_INTERNAL_UID(prefix) \
+  THREAD_CHECKER_INTERNAL_CONCAT(prefix, __LINE__)
+
+#if DCHECK_IS_ON()
+#define THREAD_CHECKER(name) base::ThreadChecker name
+#define DCHECK_CALLED_ON_VALID_THREAD(name, ...)                 \
+  base::ScopedValidateThreadChecker THREAD_CHECKER_INTERNAL_UID( \
+      scoped_validate_thread_checker_)(name, ##__VA_ARGS__);
+#define DETACH_FROM_THREAD(name) (name).DetachFromThread()
+#else  // DCHECK_IS_ON()
+#define THREAD_CHECKER(name) static_assert(true, "")
+#define DCHECK_CALLED_ON_VALID_THREAD(name, ...) EAT_STREAM_PARAMETERS
+#define DETACH_FROM_THREAD(name)
+#endif  // DCHECK_IS_ON()
+
+namespace base {
+
+// Do nothing implementation, for use in release mode.
+//
+// Note: You should almost always use the ThreadChecker class (through the above
+// macros) to get the right version for your build configuration.
+// Note: This is only a check, not a "lock". It is marked "LOCKABLE" only in
+// order to support thread_annotations.h.
+class LOCKABLE ThreadCheckerDoNothing {
+ public:
+  ThreadCheckerDoNothing() = default;
+
+  // Moving between matching threads is allowed to help classes with
+  // ThreadCheckers that want a default move-construct/assign.
+  ThreadCheckerDoNothing(ThreadCheckerDoNothing&& other) = default;
+  ThreadCheckerDoNothing& operator=(ThreadCheckerDoNothing&& other) = default;
+
+  bool CalledOnValidThread() const WARN_UNUSED_RESULT { return true; }
+  void DetachFromThread() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ThreadCheckerDoNothing);
+};
+
+// Note that ThreadCheckerImpl::CalledOnValidThread() returns false when called
+// from tasks posted to SingleThreadTaskRunners bound to different sequences,
+// even if the tasks happen to run on the same thread (e.g. two independent
+// SingleThreadTaskRunners on the ThreadPool that happen to share a thread).
+#if DCHECK_IS_ON()
+class ThreadChecker : public ThreadCheckerImpl {
+};
+#else
+class ThreadChecker : public ThreadCheckerDoNothing {
+};
+#endif  // DCHECK_IS_ON()
+
+class SCOPED_LOCKABLE ScopedValidateThreadChecker {
+ public:
+  explicit ScopedValidateThreadChecker(const ThreadChecker& checker)
+      EXCLUSIVE_LOCK_FUNCTION(checker) {
+    DCHECK(checker.CalledOnValidThread());
+  }
+
+  explicit ScopedValidateThreadChecker(const ThreadChecker& checker,
+                                       const StringPiece& msg)
+      EXCLUSIVE_LOCK_FUNCTION(checker) {
+    DCHECK(checker.CalledOnValidThread()) << msg;
+  }
+
+  ~ScopedValidateThreadChecker() UNLOCK_FUNCTION() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ScopedValidateThreadChecker);
+};
+
+}  // namespace base
+
+#endif  // BASE_THREADING_THREAD_CHECKER_H_